Resumen
- Predictive models developed to provide recommendations about release rates and application methods for augmentative biological control often assume a constant probability of encounter between prey and predators within plants. We tested the assumed uniform probability of encounter between the coccinellid predator Delphastus catalinae and nymphs of the sweetpotato whitefly (SWF), Bemisia tabaci biotype B (Hemiptera: Aleyrodidae), on tomato plants. We hypothesized that D. catalinae non-random search patterns would result in a spatially non-uniform intra-plant probability of predator–prey interaction that ultimately affects predation rates. Tomato plants infested with a range of 14–50 SWF adult male–female pairs were placed individually in cages and D. catalinae individuals marked with different colors were released on them. The number of SWF nymphs before and after predator release and the predator visit frequency on each leaf and leaflet were recorded. We found that the distribution of predator visits and prey mortality is concentrated towards the mid and mid-lower region of the plant canopy and followed a different within-plant distribution than that of the SWF. The resulting non-uniform probability of prey encounter presumably affected the magnitude of predation rates and the shape of the functional response at the intra-plant scale. Results show that the assumption of uniform probability of encounter among leaves within a plant could be misleading at least for predictive models of the tomato-SWF-D. catalinae system, and that spatially explicit or individual-based modeling approaches could improve prediction accuracy.